/*
 * Copyright (C) 2016 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.graph;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.graph.Graphs.checkNonNegative;

import com.google.common.annotations.Beta;
import com.google.common.base.Optional;

/**
 * A builder for constructing instances of {@link MutableGraph} with user-defined properties.
 *
 * <p>
 * A graph built by this class will have the following properties by default:
 *
 * <ul>
 * <li>does not allow self-loops
 * <li>orders {@link Graph#nodes()} in the order in which the elements were added
 * </ul>
 *
 * <p>
 * Example of use:
 *
 * <pre>
 * {
 *     &#64;code
 *     MutableGraph<String> graph = GraphBuilder.undirected().allowsSelfLoops(true).build();
 *     graph.putEdge("bread", "bread");
 *     graph.putEdge("chocolate", "peanut butter");
 *     graph.putEdge("peanut butter", "jelly");
 * }
 * </pre>
 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 * @since 20.0
 */
@Beta
public final class GraphBuilder<N> extends AbstractGraphBuilder<N> {

    /** Creates a new instance with the specified edge directionality. */
    private GraphBuilder(boolean directed) {
        super(directed);
    }

    /** Returns a {@link GraphBuilder} for building directed graphs. */
    public static GraphBuilder<Object> directed() {
        return new GraphBuilder<Object>(true);
    }

    /** Returns a {@link GraphBuilder} for building undirected graphs. */
    public static GraphBuilder<Object> undirected() {
        return new GraphBuilder<Object>(false);
    }

    /**
     * Returns a {@link GraphBuilder} initialized with all properties queryable from {@code graph}.
     *
     * <p>
     * The "queryable" properties are those that are exposed through the {@link Graph} interface,
     * such as {@link Graph#isDirected()}. Other properties, such as
     * {@link #expectedNodeCount(int)}, are not set in the new builder.
     */
    public static <N> GraphBuilder<N> from(Graph<N> graph) {
        return new GraphBuilder<Object>(graph.isDirected()).allowsSelfLoops(graph.allowsSelfLoops())
                .nodeOrder(graph.nodeOrder());
    }

    /**
     * Specifies whether the graph will allow self-loops (edges that connect a node to itself).
     * Attempting to add a self-loop to a graph that does not allow them will throw an
     * {@link UnsupportedOperationException}.
     */
    public GraphBuilder<N> allowsSelfLoops(boolean allowsSelfLoops) {
        this.allowsSelfLoops = allowsSelfLoops;
        return this;
    }

    /**
     * Specifies the expected number of nodes in the graph.
     *
     * @throws IllegalArgumentException if {@code expectedNodeCount} is negative
     */
    public GraphBuilder<N> expectedNodeCount(int expectedNodeCount) {
        this.expectedNodeCount = Optional.of(checkNonNegative(expectedNodeCount));
        return this;
    }

    /** Specifies the order of iteration for the elements of {@link Graph#nodes()}. */
    public <N1 extends N> GraphBuilder<N1> nodeOrder(ElementOrder<N1> nodeOrder) {
        GraphBuilder<N1> newBuilder = cast();
        newBuilder.nodeOrder = checkNotNull(nodeOrder);
        return newBuilder;
    }

    /** Returns an empty {@link MutableGraph} with the properties of this {@link GraphBuilder}. */
    public <N1 extends N> MutableGraph<N1> build() {
        return new ConfigurableMutableGraph<N1>(this);
    }

    @SuppressWarnings("unchecked")
    private <N1 extends N> GraphBuilder<N1> cast() {
        return (GraphBuilder<N1>) this;
    }
}
